1. Field of the Invention
The invention relates to a "universal" rack, that is one capable of housing any combination of standard type subracks containing telecommunication equipment, said rack consisting of at least one metallic upright and a number of brackets which have one horizontal suspension base for the subrack modules and two side ribs and which are adapted to be snap-inserted into said upright.
2. Statement of the Prior Art
So called "slim" racks, that is very narrow ones and hence of little encumbrance, consisting of one upright and a series of brackets arranged on said upright, are known; in conventional racks each side rib of a bracket is shaped as a trapezium with the shorter base shifted to one end, and it has a hole on the portion protruding from the longer side in common with the supporting base of the bracket and one pin near the shorter base.
To fix ideas better and now, FIG. 1 is a schematic partial perspective view of a conventional bracket ME which can be coupled to an upright MO, by snap insertion; to this end, the bracket ME has two side ribs SA, SA' protruding downwards from the longitudinal sides L1-L1' of the suspension base for the subracks (not shown).
Each rib SA has one circular notch I on the upper edge protruding beyond the transverse side Lt of bracket ME, and one outwardly protruding pin P on the lower part or shorter base of the trapezium forming the rib.
Correspondingly, upright MO is made up of two L-shaped elements or, as in FIG. 1, a single C-shaped element consisting of a rear wall 1, two side walls 2-2', and two ledges 3-3' used for supporting connectors CO.
To snap-insert the bracket into the upright MO the latter is provided with one inwardly protruding pin PS and one hole FO on each of the side walls 2--2'.
Pins PS are such as to correspond with the notches I of bracket ME, and holes FO of upright MO are such as to correspond with pins P of bracket ME.
Bracket ME was mounted by engaging the notches I of bracket ME on the upright pins PS and the bracket pins P into the upright holes FO.
In each specific case, that is depending on the composition of the subrack assembly to be mounted, connectors CO were fixed by first drilling and then threading holes 5--5'.
In other words, the connectors could be fixed only by doing on the ledges (originally virgin) some extra-working involving the drilling and threading of holes 5 according to the structural dimensions of the connectors.
Among the main drawbacks of this method, a few are mentioned below;
1. The rack can only house subracks of specified dimensions, which makes the management of rack-codes more difficult; PA1 2. The fixing of connectors involves "a posteriori" operations which are complex and costly (since they also require threading). PA1 1. A specialized structure is required for the construction of different types of racks, which increases management difficulties and very much limits system flexibility. PA1 2. A high cost results especially from the difficulty of mechanizing the drilling and threading operations on this type of rack structure. PA1 3. The bracket-supporting pins, which are made of inox steel, when fitted into the aluminium structure give rise to an intermetallic couple (inox. steel-aluminium) which is incompatible under particular ambient conditions (high humidity, saline fog, etc.). PA1 4. The width of the rack structure does not comply with the probable specifications to be issued by the CEPT, which is oriented toward an installation pitch of 120 mm.
Just to furnish a quantitative example, the previous racks could house subracks of the following modular heights: 120, 150, 200, 300, 400 mm.
Excluded from these modules were, for instance, subracks that are very frequently used, such as those with heights of 420, 240, 180 mm and so on.
It should also be noted that, due to the current trend toward miniaturization, the subrack dimensions tend to change constantly so that the need for racks capable of housing the highest possible number of subracks becomes more and more impelling.
Furthermore, said conventional racks were generally made of extruded aluminium.
Among the major disadvantages of extruded-aluminium construction we may mention the following: